Is it possible, asks Peta Bee, that being super-fit lessens the risks of smoking?

It's easy to view super-fit runners who spend hours each week pounding pavements as vice-free obsessives, but this is not always the case. A recent poll conducted by Runner's World magazine in America revealed that 6% of the 2,500 runners who responded smoked regularly, 2% of them in secret so their jogging buddies would not find out.

Even more surprising, perhaps, is that Bart Yasso, the magazine's chief running officer, says the results were not entirely unexpected. Yasso, who quit years ago, says he knows plenty of athletic types who smoke. "They are very secretive," he says. "I know they are not proud of it. These are people you would never have guessed were smokers." And it's not just runners. Other sports have more than their fair share of nicotine addicts.

In football, the habit has been rife for decades. Earlier this summer, Wayne Rooney was pictured enjoying a cigarette in a Las Vegas swimming pool, while England goalkeeper David James confessed, in his newspaper column, to a 15-year, 20-a-day habit. "I spent most of my career puffing away on fags: after training, before matches and even on the team coach," he wrote. Former French international and Manchester United player Fabien Barthez was a high-profile smoker, as was Socrates, the former Brazilian captain, who allegedly smoked two packets a day during his playing career and continued to do so in retirement, even though he was training to become a medical doctor.

Even some Olympic competitors are at it. While smoking is banned in the Olympic Village, there are designated smoking areas. "I'd say 70 out of a hundred athletes smoke," said Giorgio de Luca, an Italian weightlifter, of his fellow competitors at the Beijing Olympics this year. While that figure is almost certainly an exaggeration, there are some sports in which many competitors, such as de Luca, routinely calm their pre-event nerves by lighting up. Shirley Strong, a British hurdler who won a silver medal in the 1984 Los Angeles Olympics, admitted to having a regular post-race cigarette. Excuses abound as to why people in sport feel the need for nicotine. Some claim they need to smoke as it helps to keep their weight down. Others mistakenly believe it "opens up the lungs" and helps them to relax.

Certainly, for those who can't give up, exercise offers some protective effects against the well-documented risks of cigarette smoking. In a 2006 study published in the journal Cancer Epidemiology Biomarkers and Prevention, scientists from the universities of Minnesota and Pennsylvania showed that women who were current or former smokers and who also did high levels of physical activity were less likely to suffer from lung cancer than sedentary ex-smokers. "When you exercise, that improves your cardiovascular function and your HDL cholesterol and generally it's just good for you," says Stanton Glantz, a professor of medicine in the cardiology department of the University of California, who has also been studying the links. "So if you smoke and exercise you are going to be better off than if you smoke and don't exercise."

Not surprisingly, though, smoking does not enhance athletic performance. "The main problem is that the carbon monoxide it produces in the body displaces oxygen from haemoglobin, the red blood cells that transport oxygen to the muscles in exercise," says Jackie Dabinett, director of the sport, performance and rehabilitation centre at Roehampton University. "In the short term, that will result in decreased performance across most sports, but particularly in endurance-based activities. In the long term, smoking narrows the airways and causes damage to the lungs that limits the amount of oxygen in the body at all times." While the cardiovascular system is worst hit, there is some evidence that long-term smoking also leads to a decrease in muscle strength and volume of muscle fibres, affecting both speed and power.

The longer someone smokes, the more serious the risk of conditions like emphysema, bronchitis and lung cancer become, Dabinett says. If you quit, things can improve within days. Even the inflammation that is caused to lung tissue is reversible. One study in the journal Medicine & Science in Sports & Exercise found that smokers had better oxygen concentration levels and were able to extend their exercise time only a week after quitting. "It really depends on how much someone smokes, how long they have been smoking and also on their body's genetic ability to deal with the damage it causes," Dabinett says. "Just a few cigarettes a day can be seriously damaging, but not as damaging as a 30-a-day habit."

There are always exceptions to the rule, however. Simon Garner, a former professional footballer who played for Blackburn Rovers and West Bromwich Albion in the 80s and 90s, was a smoker when he first signed for Blackburn, aged 16. "It didn't go down well with my coaches and managers, but I carried on and I went on to become Blackburn's all-time leading League goalscorer," he says. "As long as I was scoring goals, they put up with me being a smoker. One of them, Kenny Dalglish, even suggested it might adversely affect my performances if I gave up."

Garner, now a journalist, says he knew of "plenty of players who enjoyed a crafty fag, but never in public". Towards the end of his career, he signed for Wycombe Wanderers and was asked to do a lung capacity test, a measure of aerobic fitness and ability, with the rest of the squad. "There were 20 other players of various ages, ranging from 18 to 35 years who took part," Garner says. "The biggest shock was that I was the old smoker and came out with the best lung capacity of them all."